A stud welder is known from U.S. Pat. No. 2,816,210, for example, which describes a tool through a tube of which the studs are fed in succession to a chuck, collet or holder at the end of the tube. A detent is generally provided in the chuck, which can be removable and replaceable, and which, once passed by the advancing stud, serves to prevent reverse movement of the stud relative to the tube past this detent.
In the arrangement disclosed in this patent, the detent is mounted on the chuck and for the positioning of a stud in the chuck, the latter is retracted into a rearmost position together with the feed passage, a stud is advanced to the chuck for example by compressed air so that it passes the detent and then is blocked from reverse movement, and the chuck is advanced with the leading end of the stud projecting therefrom until it engages the workpiece or support relative to the housing within which the chuck is movably mounted.
During this movement and as the stud is pressed against the workpiece or support, the detent continues to engage the stud as an essential positioning element and as a means for applying pressure to the stud against the workpiece.
The detent thus extends through a bore which is at a right angle to the longitudinal dimension of the chuck and is movable.
For the detent to function, it must apply considerable mechanical force to the stud and thus undergoes significant mechanical stress in turn so that wear is an important problem.
Since the detent maintains contact with the stud during the welding action, the welding current is applied at least in part through the detent and contact resistances can cause electric arcs to jump between the detent and the stud which can cause deterioriation of the detent and/or its guideway and thus be detrimental to the appropriate movement of the stud.
Furthermore, since the detent is usually provided to engage the edge of the stud, it is possible that a stud is relatively short (e.g. when the axial length of the stud is equal of less than its diameter as is frequently desired), a tilting or canting of the stud can occur relative to the detent to block the operation of the device and require dismantiling or other corrective means.
Not only is there a danger that a stud may become misaligned within the device to block its operation, but there is always the danger that misaligned studs will not be welded with positional accuracy or orientation to the workpiece or support.